West London bathed in tropical temperatures yesterday as a blast of warm air from Spain saw the temperatures rise to almost 30 degrees C on the hottest day of the year so far.

It was so hot that employers were urged to let staff wear shorts to help them cope with the heat.

And forecasters have warned that today could get even HOTTER with temperatures as high as 32C in the south east with the Midlands and north west England nudging 30C.

Public Health England has issued a Level 2 alert and Brits have been warned to stay indoors or hit the shade between 11am and 3pm today.

Despite the warnings sun-worshippers have raided supermarkets for meat, barbecues and beer for the predicted hottest day of the year today - and bookies Ladbrokes have even paid out already on this year being the hottest summer on record.

Despite the heat, paramedics say they have been called out to a number of incidents of children being left in baking hot cars.

Tony Heselton, lead paramedic with South Central Ambulance service warned: “Please never leave your children or pets in the car - even short periods of time with the windows open slightly can cause the temperature in your car to rise to over 50C in a matter of minutes.

“This can cause heatstroke, dehydration and even death.”

And the TUC issued a plea for employers to let staff wear shorts at work.

"Now is the time for employers to relax the dress code rules temporarily and allow their staff to dress down for summer."

The Red Cross says in the UK a heatwave is generally when the temperature exceeds 30°C during the day and 15°C at night on consecutive days.

The last heatwave in 2009 saw an extra 300 heat-related deaths and Public Health England has warned the elderly and unwell to stay indoors.

Director for health protection Dr Paul Cosford said: “While many people enjoy hot weather, high temperatures can be dangerous, especially for people who may be particularly vulnerable such as older people, young children and those with serious illnesses."

Meanwhile steaks, sausages and strawberries flew off the shelves yesterday with Tesco expecting to sell 25 million bottles of beer and three million bottles of wine.

Emily Stuart, stock manager at Tesco, said: “Over the last 10 years barbecuing has grown into one of the great social occasions.

“It looks like most of the country will be cooking up a storm in their gardens this weekend thanks to the promise of the first prolonged stretch of brilliant weather.”

The store said it expects to sell one million packets of sausages, 250,000 steaks, 150,000 barbecue chicken packs and 1.2 million cucumbers.

Met Office spokesman Dan Williams said: “The real story on Friday is the heat - we’re looking at 32C in London and 30C in central England as well.

“It’s going to be pretty uncomfortable with the heat and will make its way up to Manchester and the north west.

“It’s hot and muggy pretty much everywhere.

“Then we’ll see the Spanish plume with cool air from the Atlantic forcing the warm air to rise on Saturday and unleashing thundery showers.”

Yellow ‘be aware’ alerts for rain are in place for most of England and Wales on Saturday with the Environment Agency warning of flooding.

Storms are expected to move from northern Spain, across France before reaching southern England after midnight on Friday.